In general, an airbag module is installed in a vehicle in order to protect a driver and an occupant when a collision accident occurs while the vehicle travels. The airbag module may be classified into a driver seat airbag that is provided in a steering wheel of the vehicle, which is disposed in front of a driver seat, in order to protect a driver, a front passenger seat airbag that is provided in a dashboard, which is disposed in front of a front passenger seat, in order to protect an occupant seated on the front passenger seat, and a variety of other airbag modules for protecting the occupant, and may be classified into a curtain airbag module, a seat airbag module, and the like depending on installation positions of the airbag module.
FIG. 1 is a side view illustrating an example of an appearance in which a front passenger seat airbag module for a vehicle according to the related art is deployed.
As illustrated in FIG. 1, a front passenger seat airbag module for a vehicle according to the related art is installed to be concealed in a dashboard, and includes an inflator 5 which generates high-pressure gas when a non-illustrated impact detection sensor senses set impulse at the time of a vehicle collision, and an airbag cushion 10 which is deployed toward an occupant seated on a front passenger seat while being filled with high-pressure gas.
The airbag cushion 10 is deployed at a very high speed toward the occupant seated on the front passenger seat while being guided by a wind shield glass within a range that the airbag cushion 10 does not break the wind shield glass when the airbag cushion 10 is deployed.
Meanwhile, in order to prevent the occupant from being injured due to the airbag cushion 10 when injection gas is excessively injected and the airbag cushion 10 is deployed toward the occupant seated on the front passenger seat at a high speed, a vent hole, which discharges a predetermined amount of gas from the inside to the outside of the airbag cushion 10 at the same time as being fully filled with gas for deployment, is formed in the airbag cushion 10. A plurality of vent holes may be formed in a side portion of the airbag cushion 10 except for a portion that is shielded by the wind shield glass. The reason is that in a case in which the vent hole is shielded by the wind shield glass, a function of the vent hole cannot be performed.
However, recently, high-pressure gas is excessively discharged through the plurality of vent holes to decrease internal pressure of the airbag cushion such that an original function of mitigating impact cannot be performed, and severity of a head injury to the occupant has increased. As illustrated in FIG. 1, in order to reduce the aforementioned head injury to the occupant, a device (hereinafter, referred to as “a vent hole opening unit 1”, for convenience of description), which shields the vent hole using a vent hole cover, and then cuts a tether, which holds the vent hole cover, using force generated when the airbag cushion is fully deployed, such that the vent hole cover opens the vent hole, is added.
The front passenger seat airbag for a vehicle according to the related art has resolved the head injury to the occupant to a certain degree using the vent hole opening unit 1, but consequently, the severity of a neck injury to the occupant, which is an important item in the United States New Car Assessment Program (US-NCAP), is rather decreased.
In order to apply the vent hole opening unit 1, the general vent hole 2 needs to be formed to have a small size in order to prevent internal pressure of the airbag cushion from being excessively decreased due to another vent hole (referred to as ‘a general vent hole 2’ for convenience of description) which is irrelevant to the vent hole opening unit 1. However, at the time of an unbelted regulation test (that is, this test is performed without fixing a dummy using a seat belt), actually, the vent hole opening unit 1 is not frequently operated, and the internal pressure of the airbag cushion 10 is excessive because of an influence of the general vent hole 2 having a small size, which may cause a head injury and a neck injury to the occupant. On the contrary, when the vent hole opening unit 2 is operated, there is a problem in that internal pressure of the airbag cushion 10 becomes significantly low.
The reason is that despite the fact that a maximum time point when the occupant has a head injury precedes a maximum time point when the occupant has a neck injury, the vent hole opening unit is operated at the same time when the airbag cushion 10 is fully deployed at the time of the unbelted regulation test.